voltage regulator on most subaru is controlled by the ecu , if yours is, get it checked, often it is bad or weak connections and bad ground by the battery, add a good ground form battery to body
On my Forester the voltage regulator is in the alternator. I will have the grounds checked.
I've never heard of that many failed alternators! No failures on either of our Foresters.
The voltage regulator is part of the alternator, it is mounted internally. The voltage regulator monitors the battery voltage thru lead  on the connector, thru fuse #3 in the engine compartment fuse box. Lead  on the connector is only used to light the "charge" light in the combination meter... instrument panel. Note that the "charge light" is an incandescent bulb, which can burn out.
The alternator grounding to the engine occurs thru the alternator body, thru the mounting hardware. Aluminum will form a coating that can prevent proper grounding. In addition, all the mounting/adjusting hardware needs to be tight, or proper grounding will not occur.
The earlier models are know to have insufficient grounding, so many member add additional grounding. We did this on our Foresters.
Before adding additional grounding, if you choose to, check the existing grounds.
• Lift off the grounds.
• Check for corrosion, clean if present.
• Coat with dielectric grease, I use NO-OX-ID A, which is a heavier body grease.
• Reconnect the ground. Add a washer &/or lock washer if needed.
I posted the Power Supply Routing wiring diagram on this post
in another thread discussion.
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